The present invention relates to a valve case to which an oil control valve (OCV) is attached that controls supply and drainage of hydraulic pressure to and from a variable valve actuation mechanism of an internal combustion engine, and to a resin cylinder head cover having such a valve case.
In a case where a hydraulically operated variable valve actuation mechanism is provided for a timing sprocket or a timing pulley of an internal combustion engine, hydraulic pressure supplying/draining oil passages from the oil control valve to the variable valve actuation mechanism are normally formed through a camshaft.
For such a case, for example, a configuration has been proposed in which an oil control valve is attached to the inner surface of the cylinder head cover, and the oil control valve controls supply and drainage of the hydraulic pressure through oil passages in a cam cap and the oil passages in the camshaft.
However, according to the configuration in which the oil control valve is accommodated inside the cylinder head cover as described above, the height of the cylinder head cover is increased by a space necessary for accommodating the oil control valve. This undesirably increases the size of the internal combustion engine. Therefore, a technique has been proposed in which an oil control valve is accommodated in a valve case attached to the cylinder head cover to cover an opening formed in the upper wall of the cylinder head cover (for example, see Japanese Patent No. 3525709).
If the cylinder head cover and the valve case configured as described above are formed with resin to achieve the weight reduction, since the rigidity of resin is generally lower than that of metal, the cylinder head cover may be distorted or deformed when attaching the cylinder head cover to a cylinder head. This may, in turn, affect the valve case.
The dimensional accuracy of the attaching portion to which the oil control valve is attached may be decreased due to such distortion or deformation. Thus, the oil control valve may not be properly attached to the attaching portion or the oil control valve may malfunction.